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Why Sleep Matters

"Sleep is a biological imperative," says Stuart Quan, M.D., a Harvard Medical School professor of sleep medicine and editor of the Journal of Clinical Sleep Medicine. "You can't not sleep," he says.

Virtually all animals sleep. Fruit flies have been shown to have sleep cycles, and even sea sponges have sleeplike periods, Quan says. While experts have different theories on why we sleep, it's well proven that getting too little has serious consequences for your health and diabetes. Shorting yourself on shut-eye can worsen diabetes and, for some people, even serve as the trigger that causes it.

People who don't sleep enough may:

-- impair the body's use of insulin.

-- have higher levels of hormones that cause hunger.

-- crave junk food.

No snooze, you lose

People who don't get enough sleep often have higher levels of chronic inflammation and insulin resistance. Lack of sleep also can increase production of cortisol (the body's primary stress hormone), impair memory and reflex time, elevate blood sugar, and increase appetite -- ultimately promoting weight gain, says Carol Touma, M.D., an endocrinologist at the University of Chicago who focuses on sleep research and metabolism.

And the more you weigh, the worse you sleep. Research by Madhu H. Rao, M.D., an endocrinologist at the University of California, San Francisco, found that a person's body mass index (BMI) affects slow-wave sleep, the deep sleep cycles needed for maximum rest. Very preliminary results of Rao's current research on the effects of sleep restriction in healthy volunteers show an increase in insulin resistance in the range of 10 to 15 percent. But mysteries remain.

Will sleeping more help?

Lack of sleep may harm your body and worsen diabetes, but there is no evidence that increasing sleep (to more than eight hours) can improve diabetes control. One reason, Rao says, is because it's more difficult to extend people's sleep during a research study than to restrict it.

Also, most of the studies evaluating diabetes control and sleep have looked at treating people with both diabetes and sleep apnea with a continuous positive airway pressure (CPAP) machine to see if blood sugars improve, Touma says. None of these studies has shown an improvement, she adds, but no study has required CPAP to be used all night. "There are some very promising studies looking at blood sugar control with CPAP use for the entire duration of the night," Touma says.

Eight is the magic number

Studies show that getting six to eight hours of sleep a night is best for your body.

"That's the sweet spot," Rao says. But there is no exact formula for how much sleep each person needs. The average American sleeps about six hours and 40 minutes a night, down nearly two hours from the previous decade.

If you have trouble falling asleep, try sticking to a regular schedule. Get up and go to bed around the same time to regulate your body's sleep-wake cycle. Rao tells her patients to limit distractions before heading to bed. Turn off the computer, turn off the phone, and relax. "It's hard for me, hard for patients, hard for everybody," she says.

So how much sleep does Rao get? "Not as much as I should," she says with a laugh.